1. Field of the Invention
The present invention relates to disk drives. More particularly, the present invention relates to a disk drive comprising a programmable inverting voltage regulator configured relative to the disk drive""s mode of operation.
2. Description of the Prior Art
The preamp in a disk drive requires positive and negative supplies. The negative supply is generated by inverting the positive supply within the disk drive using an inverting voltage regulator. The inverting voltage regulator is typically implemented as a switching regulator. A switch is switched on in order to apply the positive supply to an inductor to charge the inductor with current, and then switched off to discharge the energy stored in the inductor into a capacitor to generate the negative supply. It is desirable to minimize the power consumption of the inverting voltage regulator, particularly in mobile applications, as well as minimize the noise induced in the read signal by the switching regulator. Further, it is desirable to minimize the size of the inductor and capacitor in order to reduce the cost of the disk drive.
There is, therefore, the need for a more efficient inverting voltage regulator which reduces noise in the read signal. Further, there is a need for an inverting voltage regulator employing a smaller, less expensive inductor and capacitor for use in generating the negative supply for a preamp in a disk drive.
The present invention may be regarded as a disk drive comprising a disk, a head actuated radially over the disk, and a preamp for supplying a write current to the head during a write mode and for amplifying a read signal generated by the head during a read mode. The disk drive receives a non-inverted voltage supply having a first polarity and comprises a programmable inverting voltage regulator (PIVR), responsive to the non-inverted voltage supply, for generating an inverted voltage supply having a polarity opposite the first polarity, the non-inverted and inverted voltage supplies applied to the preamp. The disk drive further comprises a controller for generating a control signal to configure the programmable inverting voltage regulator relative to at least the read and write modes.
In one embodiment, the PIVR comprises an inductor, a capacitor, and a switch comprising a first state and a second state, the first state for applying the non-inverted voltage supply to the inductor to generate a current in the inductor and the second state for disconnecting the non-inverted voltage supply from the inductor to discharge the current into the capacitor to generate the inverted voltage supply. The PIVR further comprises a diode for isolating the non-inverted voltage supply from the inverted voltage supply, and a current sensor for sensing the current in the inductor and for generating a current sense signal. A hysteretic comparator within the PIVR controls the state of the switch by comparing the current sense signal to a first threshold and to a second threshold. The hysteretic comparator configures the switch into the first state when the current sense signal exceeds the first threshold and into the second state when the current sense signal exceeds the second threshold, wherein the first threshold is substantially different than the second threshold. At least one of the first and second thresholds is programmably configured by the controller relative to the disk drive""s mode of operation. A voltage comparator within the PIVR disables the hysteretic comparator when the second voltage supply exceeds a third threshold.
In one embodiment the first and second thresholds are generated using current sources. In an alternative embodiment the first and second thresholds are generated using voltage sources.
In one embodiment the hysteretic comparator comprises a programmable resistor for programming the at least one of the first and second thresholds.
In yet another embodiment, the switch, current sensor, and hysteretic comparator are implemented in an integrated circuit, and the inductor and capacitor are implemented external to the integrated circuit.
The present invention may also be regarded as a power driver integrated circuit (IC) for use in a disk drive. The disk drive comprises a disk, a spindle motor for rotating the disk, a head, a voice coil motor (VCM) for actuating the head radially over the disk, and a preamp for supplying a write current to the head during a write mode and for amplifying a read signal generated by the head during a read mode. The power driver IC comprises an input for receiving a non-inverted voltage supply having a first polarity, circuitry for generating control signals applied to the spindle motor and VCM, and a programmable inverting voltage regulator (PIVR) responsive to the non-inverted voltage supply. The PIVR for generating an inverted voltage supply having a polarity opposite the first polarity, wherein the non-inverted and inverted voltage supplies for use by the preamp. The PIVR is configurable relative to at least the write mode and the read mode.
The present invention may also be regarded as a programmable inverting voltage regulator (PIVR) for use in supplying an inverted voltage supply to a preamp in a disk drive. The PIVR comprises an input for receiving a non-inverted voltage supply, an inductor, a capacitor, and a switch comprising a first state and a second state, the first state for applying the non-inverted voltage supply to the inductor to generate a current in the inductor and the second state for disconnecting the non-inverted voltage supply from the inductor to discharge the current into the capacitor to generate the inverted voltage supply. The PIVR further comprises a diode for isolating the non-inverted voltage supply from the inverted voltage supply, and a current sensor for sensing the current in the inductor and for generating a current sense signal. A hysteretic comparator within the PIVR controls the state of the switch by comparing the current sense signal to a first threshold and to a second threshold. The hysteretic comparator configures the switch into the first state when the current sense signal exceeds the first threshold and into the second state when the current sense signal exceeds the second threshold, wherein the first threshold is substantially different than the second threshold. A voltage comparator within the PIVR disables the hysteretic comparator when the second voltage supply exceeds a third threshold.